Pilot valve for compressors



Feb. 26 1924. 1,484,674

5. B. REDFIELD PILOT VALVE FOR comranssons Filed may 16. 1923 INVENTOR e'e kl Patented Feb. 26, 1924.

UNITED STATES PATENT OFFICE.

SNOWDEN B. REDFIELD, 01 EABTbN, PENNSYLVANIA, ABBIGNOB TO INGERSOLL-RAND COKPANY, OI JERSEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY.

* PILOT VALVE FOR COMPRESSOR.

Application filed Kay 16,

To all whom it may concern:

Be it known that I, Snowman B. RED- FIELD, a citizen of the United States, a resident of Easton, county of Northampton, and State of Pennsylvania, have invented a oertain Pilot Valve for Compressors, of which the following is a specification, accompanied by drawing.

This invention relates to compressors, but more particularly to pilot valves for compressor regulators.

Valves heretofore used for controlling the o erationof compressor regulators, especially starting unloaders, have fre uently proved inefiicient and unreliable for t e rea son that they have broken in a short time after installation, or have failed to operate the unloader positively to relieve the compressor of its load or to throw on the load at the proper time.

The objects of this invention are to overcome the above difficulties by roducing a valve mechanism which is simp e in its construction and which will 0 erate the unloader roperly and positive y onstarting, and entirely relieve the compressor load on stopping.

Further objects of the invention will hereinafter appear, and to all of these ends the invention is shown .in the accompanying drawin in which,

The ure is a vertical sectional view in elevation of a compressor unit with the unloader and 'pilot valves connected thereto, the parts being shown in running position.

Referring to the drawings, the unloader A is connected to the discharge line B of a compressor C between the compressor and the usual receiver D. The compressor comprises the cylinder E having the reciprocating piston F, adapted to be driven by any suitable source of power, as an electric motor (not shown). The compressor is provided with inlet valves G, the discharge valves H, and the discharge chamber J connected to the discharge line B.

The unloader comprises the valve casing K having the main valve chamber L separated from the outlet 0 by a partition P on which the main check valve Q is adapted to be seated for controlling the discharge from the casing. The check valve Q- is provided with the spring R bearing on tlhe a so forms a valve guide. The pressure in the ma. Serial itojeaaaai.

receiver tank D normally holds the main check valve Q to its seat when the compressor is idle.

The wall T of the casing K is provided with a valve seat U on which the relief valve V is adapted to be seated for controlling communication between the main valve chamber L and the atmospheric vent X, conveniently located in the side of the extension Y of the main casing K, in which the relief valve V operates. The relief valve V is preferably carried by a piston Z and has limited longitudinal movement relatively to the piston, being urged outwardly from the piston Z by a comparatively hea coiled spring a in the valve socket b, of so ficient strength to resist the full line pres sure in the main valve chamber L and prevent the relief valve from opening from its seat U against the sprin due to said pressure when the valve is held to its seat by the combined spring pressure and fluid pressure behind the piston Z. The movement of the relief valve V is limited by the pin 0 passing throu h a transverse aperture d in the valve, an secured at each end in the piston Z. r The piston Z, of the difi'erential type, is provided with an enlarged head e a pressure area materia ly greater than the opposed pressure area when in its inward position on the face of the relief valve V, and pressure behind the piston head 6 will force the relief valve V to its seat U with sufficient force to compress the strong 5 ring a and also hold the piston head 2 rmly against the seat f in the extension Y of the casing, so that leakage of fluid ast the piston from behind the piston head is shut off and prevented. The relative longitudinal movement or lost motion provided between the relief valve V and the piston Z enables both the valve and the piston to be tightly seated on their seats U and f respectively.

A projection or stop 9 on the piston Z is adapted to bear against an adjusting screw it in the cap TV, by means of which, the initial starting position of the piston Z and relief valve V may be adjusted.

The unloader, so far described, prevents the fluid compressing load from coming upon the machine until the motor is up to full speed. During the starting period, fluid, as air, enters the main valve casing K at the forming inlet side and leaves at the'atmos heric vent X, and the main check valve Q, olds back the air in the receiver D and pipe lines. When the compressor is started, the sli htressure built up in the main valve cham r l: will force both the relief valve V and piston Z rearwardly and substantially all the air will pass out through the vent X to atmosphere. It is to be assumed that the adjusting screw it has been set at such a point that the relief valve and piston move rearwardly and open the relief valve the required amount, so that when the compressor is up to full speed there will be a throttling pressure of a few pounds as the air passes the relief valve V.

The loading of the compressor should be delayed until substantially full compressor speed is reached. and the unloading should occur automatically just as or before the compressor stops entirely. In accordance with the present invention, to enable the unloader A to operate positively and to relieve the pressure on both sides of the compressor piston F as the compressor stops I provide pilot valves which are connected to the compressor cylinder, and in series with the unloader.

In this instance, the pilot valves A and B are connected by piges (not shown) to the compressor cylinder adjacent each end thereof. A pipe or tube 16 connects the extension Y of the main valve casing rearwardly of the iston Z with the port 15 in the upper section of the pilot valve B in order to permit ressure fluid to be relieved from or admitte to the rear of the piston Z. The pilot valve A is in communication with the main valve chamber L through the pipe or tube 12, and the upper section of the pilot valve B is in communication with the port 14 of the pilot valve A by the pipe or tube 13. The unloader and pilot valves are thus connected together in series, the advantage of such a connection being that the pressure on both sides of the compressor piston is relieved as the piston stops, and movement of the unloader piston Z is positively controlled.

The pilot valve A is composed of upper and lower casing sections j and k respectively, which are held together in any suitable manner, as by bolts and nuts 0. In the upper casing section j is located a down- \vardly seating ball check valve p which controls the passage of fluid from the main valve chamber L. A coil spring 1' holds the valve 1) to its seat when the compressor is idlc. An upwardly seating ball check valve a, maintained a predetermined distance from the valve 77 by a spacer pin 1, controls the passage of pressure fluid to atmosphere through the port or vent u in the casing section 7'. The arrangement of the ball check valves 1 and s and spacer pin it is such that Imp-i4 when one valve is seated the other is unseated. A piston '12, movable in the casing section is provided with an enlarged head in, whic is adapted to be moved to its seat a: by pressure fluid from the compressor cylinder E. A plunger 3/ is located in the piston v and has limited movement therein over a pin 2, which passes through the transverse aperture 3 in the plunger. The ends of the pin a are connects to thepiston v. A comparatively heavy coiled spring 2 in the piston v normall holds the plunger y in its extreme exten ed e"position, so that when the piston 'v is mov forwardly and the enlarged head to is forced to its seat a, the plunger y will bear against and seat the ball valve 8.

The check valve 6 in the lower casing section k is provided with the small 011; 7, and controls the outlet of pressure uid to'the compressor cylinder. A coil spring 8 serves as a distance piece for the check valve 6 so that the valve will not be moved too great a distance from its seat.

The pilot valve B is similar in its construction to the pilot valve A just described, and descri tion of one pilotvalve is deemed sufficient or a clear understanding of the invention.

Assuming that the compressor is starting or stopping and the compressor piston F is moving to the left, pressure fluid is forced from the compressor cylinder through the port 17 of the casing section A: and moves the piston 'v upwardly, causing the enlarged head '20 to be seated on its seat :11, and thereby seating the ball check valve 8 to shut oil the passage of fluid from the upper casing section j to atmosphere through the vent u. At the same time, the ball check valve 8 is seated, ball check valve 9 will be unseated by means of the spacer pin t, and pressure lluid is permitted to pass from the main valve chamber L through the pipe or tube 12 into the pilot valve A, past the ball check valve 7), and to the pilot valve B through the pipe or tube 13.

As the compressor piston F is on its suction stroke relative to the pilot valve B, pressure fluid in the lower casing section passes from beneath the piston '0' through the port 18 in the check valve 19. and port 20 into the compressor cylinder E, and the piston 11' is moved downwardly by the combined action of the coil spring 1'', and the entrance of air through the port it in the upper casing section. The ball check valve 7) is seated by the coil s ring r, so that fluid ressnre from the main valve chamber L is 5 mt oil and prevented. The ball check valve a is accordingly unseated by the spacer pin t, and pressure fluid from behind the enlarged head e of the unloader piston Z passes through the pipe or tube 16 and vent u to atmosphere.

Ill

When the compressor piston moves to the ri ht on startin or stopping, the operation 0 the pilot va ves above described is reversed, and the piston r and ball valves 8' and in pilot valve B will be in then war ition and pressure fluid from he s ace ack of the piston Z will pass through t e tube 16 past the ball valve p in the pilot valve l3 through the tube 13 into the pilot valve A, past the ball valve 8, which will be in its unseated position, and out through atmospheric vent u. The ball valve in the pilot valve A will then be. in its seated position, thereby cutting off the passa e of fluid from chamber L.

uring the time that the compressor is accelerated, the alternate rising and falling of the pistons a; and e in both pilot valves will continue until the com ressor piston F has attained such a spied that there is insuflicient time during t e suction strokes of the compressor piston relative to each pilot valve alternately, for the fluid pressure in the space under the pistons c and 'v' to escape to the compressor cylinder. When this condition has been reached, fluid pressure in the space under the pistons 11 and a will be sufliclent to hold the pistons in their extreme upper position throughout the normal running period of the compressor. \Vhen the lstons are in their upward position the c eck valves 8 and s are seated, and the check valves p and p are unseated. Pressure fluid is therefore permitted to flow from the main valve chamber L through the pipe or tube 12, past the ball check valve 7) and spacer pin t in the pilot valve A, through the pi or tube 13 to the pilot valve B, past t e ball check valve 39' and spacer pin t, and through the pipe or tube 16 to the extension Y of the main valve casing. This ressure fluid forces the iston Z inward y, thereb moving the reief valve V to its seat flow of pressure fluid from the main valve ggamber L to atmosphere through the vent Further increase of pressure back of the piston Z com resses the s ri a and moves the enlarged ead-e of t e lston Z to its seat f, thereby seating both t e relief valve V and the piston Z. The relief valve V being thus closed, pressure fluid from the compressor cylinder passing into the main valve chamber L increases the pressure therein to such a point as to overcome the sprin R of the main discharge valve Q,

and uid pressure in the discharge line 0 and receiver D, raises the check valve Q, and discharges the pressure fluid from the compressor cylinder through the discharge line 0 into the receiver D.

On stopping of the compressor, during the slowin down of the iston F, suflicient time will allowed on t e suction strokes shutting ofi the relative to each ilot valve to allow the pressure fluid un er the pistons c and "0 to be discharged into the com ressor cylinder. Thus the pistons '0 an e will be rmitted to move downwardl allowing the ball check valves 8 and a to unseated and the ball check valves 12 and p to be seated. This action takes lace alternately in the two pilot valves on t e alternate suction strokes. When the check valves .9 and s are unseated, pressure fluid from behind the piston Z will be permitted to flow to atmosphere through the atmospheric vents u and u alternate y with each suction stroke of the com ressor pistons, and at the same time the ow of pressure fluid from the main valve chamber L is shut off by the alterltilate closing of the ball check valves p an 'lclhe unloaderlshould bebaidjusted to unoa as prompty as i e on etc in To this end, washer-s i l are providdd l n the lower sections of the pilot valve casings by which the volume under the pistons 17 and 'v' may be varied. With high pressures there is too great a volume of am under the pilot valve pistons '0 and c to permit quick passage thereof through the small ports 7 and 18 in the check valves 6 and 19, respectively, for the com ressor to unload before stopping. It t ere'fore becomes, necessary to remove the lower section of the ilot valve casings and insert a greater num r of washers 11 in order to reduce the space or volume into which pressure fluid may enter. On the other hand, with low pressures it is necessary to increase the space or volume in the lower section of the plot valves to prevent unloading during the running riod and to delay the unloading until t e com ressor plston F has slowed down. To 0 this, the number of washers must be reduced.

In order to prevent the parts from falllng out when the lower section k of the pi ot valve A is removed, I provide a screw 4 threaded into the upper casing section j and extending into an external circumferential groove 5 in the piston 11, thereby limiting the rearward movement of the piston 'v. The pilot valve B is provided with a similar limiting device for the pilot valve piston, as shown.

I claim:

1. A ilot valve for compressor regulators comprising a casing ada ted to be connected to the compressor cylin er, a valve for controlling the admission of pressure fluid to the casing, a valve spaced from the admis sion controlling valve for controlling an atmospheric vent in the casing, a single means for actuating the said valves in one direction controlled by the pressure in the compressor cylinder, means for moving the valves in the opposite direction, and means for varying the volume of pressure fluid admitted to the casing from the compressor cylinder.

2. A pilot valve for compressor regulators com rising a casing ada ted to beconnected to t e com ressor cylin er, a valve controlling the a mission of ressure fluid to the casing, a valve control ing an atmospheric vent in the casing and operatively connected to the admission controlling valve, whereby when one valve is seated, the other valve is unseat-ed, means controlled by the pressure in the compressor cylinder for actuating the valves in one direction, and means for returning the valves to normal position as the pressure in the compressor cylinder is reduced.

3. A pilot valve for compressor regulators comprising a casing adapted to be connected to the compressor cylinder, a valve controlling the admission of pressure fluid to the casing, a valve controllin an atmospheric vent in the casing an o eratively connected to the admission control mg valve, whereby when one valve is seated, the other valve is unseated, means controlled by the pressure in the compressor cylinder for actuating the valve in one direction, means for returning the valves to normal position, as the pressure in the compressor c linder is reduced, and means for varying tie volume in one part of the easing into which fluid pressure is admitted whereby the movement of said actuating means is controlled.

4. A pilot valve for compressor regulators comprislng a casing adapted to be connected to the compressor cylinder, a valve controlling an atmospheric vent in the casing, a valve controlling the admission of pressure fluid to the casing, means for maintaining said valves a predetermined distance apart, actuating means for the said valves controlled by the pressure in the compressor cylinder. whereby when one of the valves is seated, the other is unseated, and means for retarding the flow of fluid from the casing to the compressor cylinder.

5. A pilot valve for compressor regulators comprising a casing ada ted to be connected to the com ressor cylin er, a valve controlling the a mission of pressure fluid to the top of the casing, a valve controll ng an atmospheric vent 1n the casing, spacing means between the valves means for actuating said valves whereb when one of the valves is seated, the other valve is unseabed, and a check valve for retarding the flow of fluid from the easin to the compressor cylinder.

6. A pilot va ve for compressor regulators comprising a sectional casing ada ted to be connected to the com ressor cylin er, a ball check valve control mg the admission of pressure fluid to the u er section of the casing, means controlle y the pressure in the compressor cylinder including a piston and plunger, having limited movement in the piston for unseating said valve, and a chec valve for retarding the flow of pressure fluid from the lower section of the easing to the compressor cylinder.

A ilot va ve for compressor regulators comprising a casing adapted to be connected to t e compressor cylinder, a check valve controlling the admission of pressure fluid to the casing, a check valve controlling an atmospheric vent in the casing, a spacer pin between said valves, means controlled by the pressure in the compressor cylinder for actuating said valves m one direction, and

means for varying the volume in one part of the easing into which fluid pressure is admitted to one part of the casing, whereby the movement of said actuating means is controlled.

8. A pilot valve for compressor regulators comprising a sectional casing adapted to be connected to the compressor cylinder, a sprinsnpressed ball check valve controlling the a ission of fluid pressure into the upper section of the casing, a ball check valve controlling an atmospheric vent in the easing, a s acer pin between said valves, a piston in t e casmg, a plunger having limlted movement in the piston and adapted to bear against and seat said atmos heric vent controllin valve, a check valve in the lower section 0 the casing adapted to retard the flow of pressure fluid from the casing to the compressor c linder, and washers m the lower section 0 the casing for varying the volume .into which fluid pressure is admitted, whereby the movement of the piston and plunger is controlled.

In testimony whereof I have signed this specification.

SNOWDEN B. REDFIELD. 

